1. Field of the Invention
This invention relates generally to a system and method for determining the travel range and fuel consumption of a vehicle and, more particularly, to a system and method for determining the travel range and fuel consumption of an electric hybrid vehicle, such as a fuel cell hybrid vehicle, where the method includes converting the current and state-of-charge (SOC) of an electrical storage device, such as a battery, on the vehicle to a virtual fuel flow and virtual available fuel, respectively, that are included as part of the calculation to determine the fuel consumption and travel range, respectively.
2. Discussion of the Related Art
Electric vehicles are becoming more and more prevalent. These vehicles include hybrid vehicles, such as the extended range electric vehicles (EREV), that combine a battery and a main power source, such as an internal combustion engine, fuel cell systems, etc., and electric only vehicles, such as the battery electric vehicles (BEV). All of these types of electric vehicles employ a high voltage battery that includes a number of battery cells. These batteries can be different battery types, such as lithium-ion, nickel metal hydride, lead-acid, etc. A typical high voltage battery system for an electric vehicle may include a large number of battery cells or modules including several battery cells to meet the vehicle power and energy requirements. The battery system can include individual battery modules where each battery module may include a certain number of battery cells, such as twelve cells. The individual battery cells may be electrically coupled in series, or a series of cells may be electrically coupled in parallel, where a number of cells in the module are connected in series and each module is electrically coupled to the other modules in parallel. Different vehicle designs include different battery designs that employ various trade-offs and advantages for a particular application.
Electric hybrid vehicles typically provide a display for the vehicle driver that shows the amount of fuel that is currently being consumed and the travel range of the vehicle based on the remaining fuel. For example, in a fuel cell electric vehicle including a fuel cell stack and a battery, the fuel consumption and range of the vehicle is determined by the amount of hydrogen gas fuel that has been used by the stack and the remaining hydrogen fuel stored in hydrogen pressure tanks on the vehicle.
The propulsion power for the vehicle may be provided by the fuel cell stack only, a combination of the fuel cell stack and the battery, or the battery only. For those times when the electrical power is being provided by the battery, either partially or fully, less hydrogen fuel is used to propel the vehicle a certain distance than would otherwise be used if the fuel cell stack alone was providing all of the propulsion power. Therefore, vehicle range calculations based on hydrogen fuel consumption would be inaccurate during those times when the battery power is being used to propel the vehicle.
Further, after the battery has been used to provide electric power to propel the vehicle, or otherwise, fuel cell stack power is used at the appropriate time to provide the power necessary to recharge the battery. For those times when the fuel cell stack is being used to provide electrical power to propel the vehicle and to charge the battery, the amount of hydrogen fuel consumption is substantially higher than would be required to provide the electrical propulsion only so that again the distance that the vehicle can travel based on hydrogen fuel consumption is inaccurate. Because the control system is continually changing the percentage of power provided between fuel cell stack and the battery to provide efficient operation of the vehicle, there is a large degree of oscillation between whether hydrogen fuel consumption provides too long of a distance or too short of a distance for an accurate vehicle range.